Depends what you want to do with the bike, i prefer xc and tbh theres nothing taxing round rivington unless you go into the china gardens, where your not supposed to anyways and a few gnarly bits near the pike (not the descent of the pike a grass verge just round the corner). All i can say is that i really like, but then again i suppose i have to
And the frame weights are a lie tbh when you consider the dropouts add an extra 150g. What type of riding do you like to do? cos that'll help you make your deciscion.

Edit: I run a 120mm stem with 580mm bars , 100mm sid teams, hope pro 3 xc6 and full xtr, racing ralph on the back and rocket ron up front both 2.1s hope that helps.

I have a carbon 456 and am very happy with it on 140mm forks. With light wheels and kit, I think you will build a good do-it-all bike for everything bar serious racing (frame is 1500gms which is very light). I've also considered buying a Whippet frame to replace my super light 100mm/carbon rigid frame, but I don't like what I hear about the press BB fit. There are enough people talkin about sloppy/loose fitting BB's to put me off. I'm sure a 120mm fork would work nicely on the carbon 456, not sure about a 100mm fork tho.
You're talking about 200gms difference between the frames, which can easily be saved elsewhere.

I have a Whippet and think it is great at the price. The BB, front mech & chainset compatibility do limit your options a little and that is the only reason I'd consider a 456 over the Whippet. I have had a BB that was loose but replaced with another brand and all is well for now.

Mine is a lightweight XC bike used mostly on the South Downs. If I weren't chasing the grams a 456 would probably be the simpler option for choice of forks and the components mentioned.

If weight is important to you my medium (18) frame weighs 1374g plus 124g for dropouts and bolts = 1498g in total (kitchen scale accuracy shouldn't be far out) I've not had a 456 frame to check their actual weight.

What do you want from the bike? If you want a hardcore hardtail, slackset fitted trend barge the 456 will allow you to do that but the whippet is more limited.

The 456C is the more versatile frame and still lighter than most steel frames and at least comparable to most alloy frames. Easy to build sub 25lbs with a little thought and not needing mega bucks.

A big plus to me was that it has a proper external bb, none of this press-fit rubbish. Though I think there have been reported problems on the 456 if you want to run one of the new 'xc' double chainsets. The 456 will also be ok with forks between 100 - 150 ish, the Whippet more limited.

I ride round Riv and when you're on a hardtail you really notice the constant patter and jarring through the saddle. There are a lot of cobbled and lumpy surfaces round Riv, just lumpy enough to make it a pain in the a... quite literally.

Hi Andy, I've only just started swapping stuff over. I got the lbs to fit the slackset as it wasn't working with my homemade headset press and the line up has to be right, which wouldn't be a problem with a standard headset. I've bought a Crane Creek seatpost shim as i didn't want to buy a new seatpost until I can afford a dropper post. I've just run into a problem swapping the bottom bracket over as I can't eliminate play from the cranks without the bearings binding slightly. I'm assuming I'll need to get the bb faced but I've just started another thread on this to see if that's the STW consensus. Most other parts should go over without too many issues but the 90mm stem will have to go for something shorter at some point.

Oh and my 16" frame weighed in at 1500g on the kitchen scales including the dropouts.

1. Headset was tight to fit. I don't have a headset press, but 10 minutes cursing with a rubber mallet saw it done. I got the superstar headset with integrated top cup/external bottom cup - type 2 I think.

2. I have fitted a SLX 2x10. The rings are slightly tighter than ideal to the chain stay, but not as bad as on my old Cannondale rz. Due to the flaring at the bottom of the seat tube, a hi clamp front mech is required. I couldn't get it as low as I wanted, as the cage interfered with the chunky chainstays, but advice from the STW massive was that more clearance was acceptable/required on a double (was advised to fit it as if a 3rd ring was there) and it shifts perfectly.

3. Cable routing are a little interesting!!!

4. It works great for me with a Talas 2010 140/120/100 tapered fork. There are some issues with some tapered Rockshox apparently.

5. My seat tube had a restriction, which turned out to be the rivet from the front mech cable boss. On advice from on one, I filed this down, and all is well!!

An informed and emphatic vote for the Whippet here. I have run one SS (so can't comment on front mech, etc) for over 6 months now and i LOVE it. If you like a long-n-low position/cockpit and you're happy with the fairly steep head angle i would do it. Despite the angle, with SID RLTs up-front, it has not let me down on descents yet.

Only downside is it creaks to buggery. Every component/frame interface seems to emit noise. Not sure if it stops or i get used to it but after an hour or so of riding it seems to ease up. BB was a culprit but i have dismantled a couple of times and all seems OK + has got a little better over time. On One have reassured me that if any frame damage does develop the warranty will cover it. I just need to schedule a proper once-over in a year or so.

The creaking is really a small compromise when considered alongside the number of grins it has delivered so far. It's really nimble and acceleration is amazing. It regularly gets picked over my 3yr old much loved P7 and the full-sus that cost 3 x the Whippet!

The 456C is the more versatile frame and still lighter than most steel frames and at least comparable to most alloy frames. Easy to build sub 25lbs with a little thought and not needing mega bucks.

A big plus to me was that it has a proper external bb, none of this press-fit rubbish. Though I think there have been reported problems on the 456 if you want to run one of the new 'xc' double chainsets. The 456 will also be ok with forks between 100 - 150 ish, the Whippet more limited.

This is spot on imo. Considered the Whippet but it's the versatility of the C456...I did run it with an Alfine, now 3x9, plus I could go SS. Currently running it with Reba U-Turns 90-120...handles great. Might stick longer forks at a later date but I currently like it as a fast and light XC bike